Motion-picture film with magnetic sound track



Feb. 13, 1951 s. w. WARREN 2,541,136

MOTION-PICTURE FILM WITH MAGNETIC SOUND TRACK Filed Deo. l, 1944 2Sheets-Sheet l HHH I IIIIIIIIIIHIIII D D [I D UD D El] D l] D CI UU D DD DEUD Ulf! i] [l i] [I [I [I [111D DI] EDU D D UD 7mnnnnnnnannmmnnnnnun Feb. 13, 1951 s. w. WARREN 2,541,136

MOTION-PICTURE FILM WITHMAGNETIC SOUND TRACK Filed Dec. 1, 1944 l 2Sheets-Sheet 2 D D D D D D D D D D D D D D D D D D D D D D D D D Y. y lmmmwuummmuunmuumunmnmumumummmumnmmmmm D D D D D D D D D D D D D D D D DD D D D D D D D J a 7*."'n--S "-27% Z *lll/V111 /0 D D D D D D D D D D DD D D D D D D D D D D D D la gj Z o i mmm Patented Feb. 13, 1951MGTION-PICTURE FILMl WITH MAGNETIC SOUND TRACK Stanley W. Warren, CorpusChristi, Tex. Application December 1, 1944, Serial No. 566,142

' This invention relates to motion picture lms provided with soundtracksand it has particular reference to iilms having a sound track capable ofbeing magnetized during or after the exposure, so as to record andreproduce speech and other sounds according to Poulsens principle.

Magnetic sound tracks have very great advantages. One of the mainadvantages consists in the simplication of the sound recording and soundreproducting equipment which renders it possible, for instance, toproduce simple, inexpensive and easily manipulated amateur cameras andhome projectors for talking motion picture films, a goal which has notbeen attained to any considerable extent with films having photographicsound tracks. This simplification manifests itself also in otherrespects, as it permits reduction in bulk and weight of ambulantout-door and other lm production cameras. The magnetic equipment,moreover, is less affected by rough handling than the photographic soundfilm equipment with its photo-cell arrangement, its high tensionbatteries and its highly sensitive amplifier arrangement.

On account of these and many other advantages, endeavors to produce amotion picture iilm with a magnetizable sound track have repeatedly beenmade. These endeavors were notv successful, thus far, on account ofseveral great diiiicul-` ties associated with the manufacturing of thefilm of this type. A small number of metals only have magneticproperties in the required degree, and, therefore, metal parts such aswires, tapes, ribbons, or relatively thick metal layers on deposits haveto be united with the cellulosic material.

This more or less mechanical union of two very heterogeneous materialscould not be brought to such perfection that a usable motion picturefilm, having all the requisite properties for being handled in the usualtype of cameras and projectors and in the various preparation stages wasobtained.

One of the main difficulties experienced in connection with combinedfilms of cellulosic and metallic material consists in the lack ofuniform pliability, and of uniform expansion and contraction of thecomponents. During reeling and unreeling and during the passage of thefilm around rollers and through loops, the components detach themselvesfrom each other or become loose, thus destroying the synchronism. Thec'ementitious materials holding the metal ribbon on the film base,moreover, are unable to stand the 'strain vof an unequal shrinkage orexpansion,A which occurs to a certain extent during the s claims. (o1.27d-41.4)

chemical treatment of the emulsion after exposure.

Another difficulty is due to the unequal thickness of the combined lmand to its increased thickness, at least insome parts of its crosssection. This increase in thickness greatly impairs handling by theusual equipment and causes speedy deteriorationand destruction of thefilm. Y The primary object of the present invention is,

' therefore, the production of a motion picture lm.

with a magnetic sound track which, in spite `of the diiiiculties abovementioned, shows a uniform and satisfactory measure of pliability, acoeiiicient-of expansion and` contraction which is approximately uniformin all parts of the nlm, and` a thickness which is uniform across itsentire splicing and editing without detrimental eiects.4

It is a further object of the invention to attach the magnetic materialto, or to incorporate it into the cellulose film during the productionof the nlm `base so as to secure a perfectly unitary structure of thelm.

Many further objects and advantages are described in the followingspecication.

With these and other objects in mind, the invention consists in a motionpicture film provided with a magnetic sound track, as described in thefollowing specification, shown in the draw-` ings'and characterized inthe appended claims. It is to be understood,'however, that the inventionis not limited to the Specic examples illustrated or described inspecific terms in connection with these examples. The result may beobtained in a variety of Ways which, although not specicallyldescribed,are foreshadowed inthe Apresent application and will be clear to the:expert skilled inthe art when following the principles described, andfurther changes may be in-A troduced without in any Way departing fromthe essence of the invention.

In the accompanying drawings a number of modifications of the iilmprovided with a magnetic sound track are shown.

Figure l is a view of the upper or emulsion side of thev lm into which:a magnetic sound trac has been incorporated.

'Figure 2 is a sectional view showing a 1ongitu-. dinal section throughthe 'lm land through the:A strip-like base carrying the magnetic soundtrack;V

`2a respectively of another modification of the invention.

Figures '7, 8 and 8a are views and sectional views similar to thoseshown in Figures l, 2 and 2a respectively of another modification of theinvention.Y l

Figures 9, and 10a are views and sectional views similar to those shownin Figures 1, 2 and 2a respectively of another modification of theinvention.

Figures 11, 12 and 12a are views and sectional views similar to thoseshown in Figures 1, 2 and 2a respectively of another modification of theinvention.

Figures 13, 14 and 14a are views and ysectional views similar to thoseshown in Figures 1, 2 and `2arespectively of another modification. ofthe invention. K

Figures 15, 16 and 16a are views and sectional views similar to thoseshown in Figures l, 2 and 2a respectively of another modificationv ofthe invention.

Figurev 17 is a view of the upper side of a film provided with two soundtracks.

Figure 18 is a view of the upper side of a film provided with aplurality of sound tracks covering its entire surface. Y

In order to understand the principle governing the production of thefilm, it may iirst be mentioned that the magnetic material is eitherferro-magnetic material or an lalloyed steel, the latter being composedof soft iron, tungsten,

chromium, cobalt and other materials. The al loy is so chosen that themagnetic material, if used in the form of wire or ribbon, will have apliability and a coefficient of expansion and contraction which isadapted to the application of the same film. As an example, the alloyswhich are known under the trade names tungsten magnet steel, chromiummagnet steel, and Japanese steel may be mentioned as `alloys answeringthe requirement.

The magnetic material is first applied to a base sheet, which is alarge, thin sheet of either cellulose nitrate or cellulose acetate, thismaterial being chosen in accordance with the material of the film. Themagnetic material is placed, spread or laid on said base sheet and overthe base sheet and magnetic material a coating of dope is spread. Dopeis the Vname applied to the viscous nitro cotton solution, or viscouscellulose acetate solution, resembling honey in appearance, which isused for making the film. The solvent used is either acetone, methylalcohol', acetic acid, or another solvent such as used in filmproduction, camphor or other softening substances being added. Thesolvents evaporate and the cellulose nitrate or acetate unite withthe'base sheet of cellulose nitrate or acetate, thus locking in themagnetic material which becomes an integral part of the base sheet.

The under side of the base sheet is' now preferably treated with anetching solution called substratum,. which slightly roughens its undersur face and increases its faculty to firmly adhere to a film. 4

When the base sheet has been prepared in this way, it is cut intonarrow'strips and these are now ready to be applied to the films, whichare afterwards coated with the photographic emuls1on.

The application of these thin strips of base sheet with magneticmaterial'locked into the m0- tion picture film may be performed duringthe manufacturing of the film or at anytime during thesubsequent'preparation of the same. Of the various modificationsdescribed later, some lend themselves to the first type of application,while others are better adapted for an application to an already formedlm. When finely divided magnetic material is used, it may, of course, besprayed or flowed and enclosed in a manner to be described more fullyinconnection with the specific modification employing such granular andfinely divided material.

The application of the strips consisting of a base sheet Vwith enclosedand locked magnetic material during the manufacturing of the vfilm isperformed in the following way:

The film, as well known, is prepared from cot ton linters which arefirst cleansed and dried and are then nitrated. The nitro cotton is thenimmersed in water and is Washed, the latterstep being continued untilthe material is acid free. It is then dehydrated by means of alcoholand` dissolved in suitable solvents (acetone, methylalcohol) withsofteners like camphor added. The dopef thus obtained, consisting of theviscous nitro-cotton solution and which is a liquid of the.

consistency of honey, is now spread as a thin film by making a thin coaton a traveling surface, which, as a rule, is the surface of a largedrum, about fifteen feet in diameter and four feet across, rotatingslowly around its axis so that by the time one rotation is completed,the solvents have evaporated sufficiently to. set the film, which isthenstripped off and dried further.

It is during this stage of the manufacturing oi the film that the basesheet strips with thel locked-in magnetic material are applied.

As already stated, the base sheets carrying the magnetic material havebeen cut into thinstrips. These strips are set on rolls which are evenlyspaced for the required distance (depending on the Width of the film of8 mm., 16 mm., 35 ming), and these strips are fed to the travelingsurface as it picks up a coating of dope It will be clear that onaccount of the width of the film web during this process, a certainnumber of strips have to be fed simultaneously in spaced relation to thetraveling surface in order to provide the film web with the requiredvnumber of sound tracks, so thatl each film ultimately cut out of thefilm web shall be provided with a strip carrying the magnetic soundtrack.

In some cases metallic belts are used instead of large drums for takingup the viscose dope, but this does not affect the way of applying thebase sheet strips.

The process has been described in with nitro cellulose lms, but thepreparation of acetate films used for 8 mm. and 16 films is identical asfar as the connection withthe present invention goes.V Y

It may be mentioned that the film base, when taken from the drums andafterv having been.

dried, has a high polish and may be used or stored or-seascned untilrequired. Before being coated with the emulsion, one side is heated.with an-etching solution (substratum) that'slightly roughens the surfaceto hold the emulsion rmly,

connection The back in the case of motion picture films is coated with anon-curling coat of hardened gelatine, which equalizes the strain of theemulsion, and this coating is sov selected when a magnetic sound trackis prepared that the combined strain of the emulsion and of the magneticsound track is counteracted.

The second method of application above mentioned consists in providingan already prepared nlm with the base sheet carrying the magnetic soundtrack. In this case a shallow recess, trough or groove is out into thefilm along the edge of the motion picture film where the sound track hasto be applied. The etched side of the base sheet strip carrying themagnetic sound track material is then coated with a cement composed ofsolvents, such Ias acetone, acetic acid, methyl, alcohol, camphor, andthe like, which dissolves the material of the lm base. This coatingsoftens both the lm base and the base sheet strip and the latter is thenfirmly pressed into the recess in the groove and held there until thesolvent has evaporated.

The base sheet strip thus forms an integral part of the motion picturelm which will have no tendency to break away from the film during thereeling or rewinding operation or during its run through the projector.

. In the drawings, various methods oi providing the base sheet withmagnetic material are illustrated.

Figure 1 shows a base lm l provided with a base sheet strip 2 in whichparallel line wires 3 are embedded Iand locked in the manner abovedescribed.

The base sheet is prepared by spreading parallel iine wires evenly overthe sheet and applying the coating of dope as above described. It isthen cut into thin strips 2 shown in longitudinal section in` Figure 2and in cross section in Figure 2a. The strip 2 may be applied eitherduring the manufacturing process or thereafter.

For the modification illustrated in Figures 3, ll and 4a, iinely dividedgranular (micron) ferro magnetic material 5 is used.

The preparation of the base sheet containing the magnetic material maybe slightly different from that described. The granular and finelydivided magnetic material is mixed with the dope and the latter isspread over the base sheet and forms the desired coating. The base sheetmay now be cut into strips and applied to the film base during or aftermanufacturing, as described.

With this modification, however, another method of application of thegranular magnetic material is possible. A shallow well, groove or recessis first cut into the lm base I which is exactly of the width of thesound track 5. Dope with the distributed magnetic material is then lleddirectly into the groove, so that no base sheet need be prepared iirst.The dope unites with the nlm base l as it softens it i'lrst andafterwards, when the solvents evaporate, becomes integral with the filmbase, the granular material being locked rmly within the strip treated.

Figures 5, 6, 6a and 7, 8 and 8a. show a modication using one andtwo-wire strands 7 and 7a, respectively, arranged in parallel to thefilm, as magnetizable sound record bearers. The embedding of the wireinto the base sheet and application of strips 2 cut from the latter areprocesses identical with those already described.

Figures 9, 10 and 10a illustrate the use of a flat thin ribbon embeddedinto a base sheet strip 2. 1

Figures v11, 12 and 12a, 13, 14 and 14o and 15, 16 and 16a illustratethe use of double-back sine gle and double wire strands embedded intothe base sheet and applied to the iilm base `according to the methodsdescribed. Single or double strand wires may be doubled back as shown inFigure 11 at Ill so as to form a straight line from which bristles orshort sections i! project.

Alternatively the single or double strand wire may be bent in wave ormaeander form as shown at l2 in Figure 13. Another modification shown inFigure l5 shows a multiple wire arrangement I3 in which two wire strandswhich are doubled back, for instance, strands like those shown inFigures 11 and 13, have been combined to form two strands joined bycross sections.

All wire strands which have been doubled back may expand or contract inlongitudinal direction in a manner which follows the expansion orcontraction of the base on account of their -men mechanical structureand this expansion or contraction is not dependent upon the coeiiicientof expansion of the material of which they consist. In Figure 17 a nlm lwith a double sound track i4, i5 is shown, each consisting either of asingle wire, double wires, a ribbon, or wire strands, such as shown inany of the preceding figures. The reason for using two sound tracks i4,Hi placed symmetrically on the film on both sides of the area reservedfor the pictures is the greater mechanical strength and resistency whichmay be imparted to the film in this way. Film bases as well known, havea certain tend-l ency to warp or to buckle due to the loss or to theabsorption of moisture in the course of the chemical processes to whichthey are subjected. This causes the iilm to jump in and out of focusduring the passage of the picture aperture or of the iilm pressureplate. Moreover, when this happens at the scanning point for the soundtrack, sound reproduction is affected. The double magnetic sound trackforms a reinforcing structure preventing excess of buckling and warpingand holding the film in the correct plane.

A further modification of the invention is shown in Figure 18illustrating a modication in which the entire nlm area has been used toaccommodate a number of parallel magnetic sound tracks l1, arranged sideby side. They may be incorporated into the film base in the manner abovedescribed during the manufacturing process. The use of multiple soundtracks has been repeatedly proposed and was in some cases highlysuccessful for high fidelity reproductions feeding separate andindividually adjusted loud-speakers or banks of loud-speakers. Moreover,a plurality of sound tracks may be used to reduce to a minimumbackground noises, mechanical noises, or exciter lamp hiss which as arule cannot be completely eliminated in other types of iilm recording.

The above description will have made itclea'r that motion picture films,according to the invention, will fulll the requirements above set forthof even thickness throughout the entire cross section not larger thanabout .0055 of an inch, which is the usual thickness of motion picturefilms. The embedding and locking of the magnetic material properlyselected as regards coefflcient of expansion and pliability, willcounteract most effectively any tendency towards loos- 7 nn'g andseparation. Indeed, such a tendency would have to overcome not only theresistance offered by the :surrounding base :sheet material which infact acts .as .a unit, but also the resistance against .separation ofthe .base sheet `.from the nlm base which Ais equally strong.

Moreover, the transverse wires or `the double back Wires, on yaccount ofthe `facility to move ,the individual transversal sections, -are able toaccommodate themselves fully to any shrinkage or elongation `the basestrip may undergo, the late ter, of course, being in complete accordwith the lm base itself. It is thus seen that all the changes andvariations of `the nlm, Whether due to chemical for :mechanicaltreatment, d no longer, in a motion picture film with a magnetic soundtrack according tothe invention, provoke the strains or `stresses whichtend `to destroy or loosen the unitary structure Vof the bonded andunited components, as lwas manifestly the case in earlier endeavors toproduce a motion picture nlm With a magnetic sound track.

What I claim is: A

1. A motion picture nlm with `a magnetic sound track, comprising apicture carrying film provided with perforations and fur-ther providedwith a longitudinal `recess running along the picture carrying area `ofthe film between the latter and the perforationa a separate base stripconsisting of a material substantially identical with that of the filmand `of a length equal to that of the film, said base strip carryingferromagnetic magnetizable material embedded rwithM in it near one ofits surfaces, said base strip filling the longitudinal recess and beingheld therein with the surface -near which the magnetic material isembedded slightly protruding over the ill-m surface, said base stripbeing fixed in said recess 'by an adhesive.

'2. A motion picture film as claimed in claim l in which'the surfaceofthe base strip, near which the magnetic ymateria-1 is embedded, iscovered .by

a :coating consisting of a dried viscous solution nf' the nlm materialin a solvent.

3. A motion picture nlm with a magnetic sound track as claimed in claim1 `wherein the base strip is covered by a layer covering one of itssurfaces and consisting of a dried 4viscous solution of cellulosic lmmaterialin ra solve-nt in Whichgranular ferro-magnetic magnetizablematerial is dispersed. Y

4. A sound lm as claimed in claim 1 in which the normally picturecarrying area of the `llm is covered with a series of regularly spacedparallel recesses within which base strips with .embedded magneticmaterial Vare held and are embedded.

5. A .motion picture nlm with a magnetic sound track as specied in claim1 wherein the magnetic material consists of wire sections ein bedded inthe base sheet strip.

6. A motion picture nlm with a magnetic :sound track as specied in claim1, wherein the :magnetic material consists of a large number of parailelWire sections running transversely tothe film strip and embedded intothe base strip.

STANLEY W. WARREN.

REFERENCES CITED The following references are yof record in the file ofthis patent:

UNITED STATES PATENTS 'Loblein May i2?, 1941

